NORFOLK, Virginia -- A U.S. federal judge ordered a Somali pirate on Monday to serve a dozen life sentences in prison for his role in the hijacking of a German merchant vessel and a U.S. yacht, saying the hostage negotiator was lucky he wasn't facing the death penalty.

Mohammad Saaili Shibin is considered by U.S. authorities to be the highest-ranking pirate they have ever captured. Shibin had direct ties to those who finance pirate operations from ashore in largely lawless Somalia.

Four Americans aboard the Quest were shot to death by pirates off the coast of Africa in 2011, and the crew on the other vessel was tortured to get a higher ransom in 2010.

U.S. District Judge Robert Doumar told Shibin he was "very lucky" he wasn't facing a death sentence, although no death penalty-eligible charges were brought against him.

Prosecutors will seek the death penalty against the three men charged with shooting the Americans. Eleven other men in the case who boarded the Quest have already pleaded guilty and been sentenced to life in prison.

Shibin, who speaks several languages including English, declined to make any statements before he was sentenced.

U.S. authorities are hoping the sentence will send a message to pirates to stay away from American-flagged ships.

"I think this case explodes the myth, if still it exists out there, that pirates are some kind of romantic swashbuckling characters from Hollywood summer movies. This case showed that pirates are brutal, greedy, reckless, desperate criminals who will kidnap, torture and ultimately kill hostages in pursuit of their financial greed," U.S. Attorney Neil MacBride said after sentencing.

The yacht owners, Jean and Scott Adam of Marina del Rey, California, along with friends Bob Riggle and Phyllis Macay of Seattle, were the first U.S. citizens killed in a wave of pirate attacks that have plagued the Gulf of Aden and Indian Ocean despite a regular patrol of international warships. Negotiations with a U.S. Navy ship that was shadowing the Quest were underway when a rocket-propelled grenade was fired at it and shots aboard the yacht rang out. By the time Navy SEALs scrambled onboard the boat, the Americans had already been shot.

Shibin was convicted earlier this year of the 15 charges he faced, including piracy, kidnapping and hostage-taking. Of the 12 life sentences, 10 of them will run concurrently while two were ordered to serve consecutively. Shibin was also ordered to pay $5.4 million in restitution.

Shibin attorney James Broccoletti said he will appeal the conviction. He believes the definition of piracy may ultimately have to be decided by the Supreme Court. At issue is whether piracy can only occur if someone commits robbery at sea or whether a broader definition applies.

U.S. law refers to piracy only "as defined by the law of nations."

In May, a federal appeals court ruled in another case that an armed attack on a U.S. vessel can be considered piracy even if no one ever boards or robs the ship. In Shibin's case, he never set out to sea or boarded the Quest. Instead, he researched the victims online from shore to determine how large of a ransom to seek for them. In the case of the German ship, he didn't board it until after it had already been hijacked by other pirates and was in Somali waters.

"He's never been on the high seas and so I think that eventually the Supreme Court's going to have to decide in the modern era what is piracy, what is the law of piracy, what does one have to do to be guilty of piracy," he said.